This invention concerns a motor actuator that controls the position of a motor-driven member depending on conditions such as temperature.
In a cold storage area having a refrigerating chamber and a cold chamber separated from each other, for example, cold air in the refrigerating chamber is supplied to the inside of the cold chamber. The cold air supply is controlled by the opening and closing of a damper positioned in a passage connecting the refrigerating chamber with the cold chamber. A motor actuator is used to open and close the damper.
While the motor actuator turns on and off depending on the temperature in the cold chamber, the motor actuator can malfunction if the setting temperature for the cold chamber changes during operation. Accordingly, a stable control function is required to accommodate changes in the external conditions during operation. Further, in order to realize such a function, it is necessary that the open and closed states of the damper also be used as inputs.
Accordingly, it is an object of this invention to provide a motor actuator that prevents malfunction by employing, as an input condition, the position of the driven member, such as a damper, which is to be controlled, as well as other data, such as temperature.
Another object of this invention is to obtain stable characteristics for a motor actuator by providing an AC motor with a reverse rotation preventive mechanism to prevent possible reverse rotation upon initiation of operation.
A further object of this invention is to enable the opening and closing of a plate, such as a damper, irrespective of the driving position of the motor.
A still further object of this invention is to independently control two driven members such as dampers by a single driving source.
Yet another object of this invention is to eliminate drawbacks in conventional driving means, such as low responsive speed, larger scale of the device and noisy operation, by utilizing a motor as the driving source.